This invention relates to structural members and to parts and fitting used and for use in association therewith.
Structural members to which the invention relates may be used for the construction of permanent or temporary structures for use in what may broadly be regarded as the entertainment industry. By way of example but not limitation, such structures may be used in association with a stage for the presentation of a musical/theatrical event, for the support of a roof over a stage, for carrying lighting, sound, scenery or other production equipment, or indeed anything that may be required. In many cases such structures are temporary if an event is taking place for a short period of time, but such a structure may well be permanently installed at a location. A further example of a situation in which structural members in accordance with the invention may be utilised is an exhibition stand, but in its broadest aspect structural members in accordance with the invention may be used wherever a requirement arises therefor.
A basic element from which such structures may be assembled is a xe2x80x9ctrussxe2x80x9d, and more particularly a structural member in accordance with the invention may be such a truss. A truss characteristically comprises a number of elongate elements secured in spaced generally parallel relationship to one another by a number of transversely extending elements therebetween. The transversely extending elements are arranged to ensure that the truss is adequately strong and rigid for the loads it is intended to bear: typically some transversely extending elements extend perpendicularly to the elongate elements while other extend diagonally therebetween. Trusses particularly described hereafter are generally rectangular in transverse cross-sectional shape, with principal elongate elements at the corners of the rectangle, but generally trusses may be of other cross-sectional shapes, e.g. polygonal with more or less than four principal elongate elements. For special purposes, some trusses are able to be folded flat to occupy a minimal space for storage or transportation, and erected to an operative cross-sectional shape when required to be used. Generally, there are many known configurations of truss and the invention is applicable throughout the range of such configurations.
A structure may be created by joining a plurality of trusses together in the required configuration, using suitable connectors and fastenings as described hereafter. A structure may incorporate parts at a substantial height above a floor or ground level, and persons assembling the structure have to work at such heights. After the structure has been completed, further work will be necessary to mount other items such as lighting equipment thereon. Whilst theoretically separate access equipment should be used for safe working at a height, in practice the structure itself may be climbed upon and this brings obvious dangers in case of a fall. With this in view, a person may attach himself to a safety line which is clipped to a truss in the region in which work is taking place, but this inhibits freedom of movement and if a fall occurs may impose loads on the structure which could damage it. Add-on fall-arrest systems have been proposed, but these may interfere with the structure, imposing undue loads thereon, and generally are inconvenient.
It is broadly the object of one aspect of the present invention to address the above described problem of assisting safety of persons working at a height on a structure as above described.
According to one aspect of the invention, therefore, we provide a structural member comprising a number of elongate elements disposed in spaced generally parallel relationship to one another with transversely extending elements therebetween, wherein an element extending longitudinally of the structural member is provided with a formation extending lengthwise thereof for engagement by an attachment member to be retained to the longitudinally extending element at any of a range of positions therealong.
The attachment member may be adapted for connection to a safety element. Then it may be engaged with the formation of the elongate element in such a way as to be freely movable therealong.
Alternatively the attachment member may provide for the support of lighting or sound equipment for example to the structural member and may be intended, when engaged with the elongate element at a required position, to remain in such position.
The structural member may be generally of polygonal shape in cross-section, and some or all of the elongate elements may be disposed at the corners of such a polygonal shape. It may be at least one of said elongate elements which is provided with a respective said lengthwise-extending formation. Preferably all of said elongate elements constituting the structural member are of the same cross-sectional shape as one another, and thus each has a said formation.
The cross-sectional shape of the elements 10-13, clearly seen in FIG. 2, comprises a hollow generally rectangular box-section portion 28 and a portion 29 which defines an undercut generally T-section track formation 30 (the T-section track formation 30 shown inverted in FIG. 2). The portion 29 comprises side walls portions 31, 32 which extend generally parallel to one another from adjacent edges of the portion 28, the wall portions 31, 32 ending at inwardly-facing lip portions 33, 34 which extend towards one another to define an opening 115 therebetween. Oppositely outwardly extending recesses 116 are afforded beneath the lip portions 33, 34. The outwardly extending recesses 116 cooperate to form the cross-member of the xe2x80x9cTxe2x80x9d (which as states above is inverted in FIG. 2). Lengthwise external ribbing on the elements 10-13 is visible in FIGS. 2, 4, and 5, but omitted from FIG. 6 for clarity. Such external ribbing renders the element easier to grip and handle, to facilitate its use in erection of a structure.
Conveniently each of said elongate elements is an extrusion of an appropriate aluminium alloy. However, other materials may be suitable and it is contemplated that possibly a plastics material, e.g. fibre-reinforced, may be usable. Apart from a portion thereof having the lengthwise extending track formation, the or each elongate element may comprise a portion which is hollow, and which may be of generally square or rectangular transverse cross-sectional shape.
According to a further aspect of the invention, we provide a structure comprising at least one structural member in accordance with the first aspect of the invention as above set forth. The invention yet further provides such a structure having one or more attachment members engaged with one or more of said track formations thereof. Yet further, a safety device such as a safety lanyard may be connected to at least one of said attachment members.
Whether an attachment member is intended for connecting something to a track formation as above described at a fixed point along its length, or whether an attachment member for a safety element is movable along the track formation, engagement of such an attachment member with the track has in many cases hitherto required passing thereof lengthwise into the track from an end thereof. Similarly the attachment member has only been able to be disengaged from the track at an end thereof. Whilst this provides a high degree of safety in respect of the security with which the attachment member is held captive when it is in, for example, a mid-position along the track, it would in many cases be convenient if it were to be engageable with and disengageable from the track at such a mid-position. At the same time as providing this convenient ability, however, there should be a high degree of security against an intentional disengagement from the track.
It is broadly the object of another aspect of the present invention to provide an improved attachment member for such engagement with a track.
According to another aspect of the invention, therefore, we provide an attachment member for captive engagement with a track formation, the track formation being of undercut configuration in cross-section comprising an opening leading into respective laterally-outwardly-extending recesses at each side; the attachment member comprising a body, means adapted to extend through the opening of the track formation, and formations adapted to extend laterally outwardly generally in opposite directions into said recesses; said formations of the attachment member being movable in respect of their disposition and/or orientation between a first condition wherein they can be passed through said opening into the track and a second condition wherein they extend into said recesses to hold the attachment member in engagement with the track, there being provided locking means for retaining said formations in said second condition.
Preferably said formations engage each said recess at spaced positions along the track.
Said formations of the attachment member may be afforded by spaced generally T-shaped elements which have stem portions which, when the attachment member is engaged with the track, extend through the opening of the track, and transverse portions which extend laterally outwardly in opposite directions into said recesses of the track.
One of said T-shaped elements may be movable angularly about the axis of its stem portion relative to the body of the attachment member, whilst another may be movable lengthwise of its stem portion relative to the body of the attachment member.
The body of the attachment member may further comprise a guide portion which extends lengthwise of the body, for disposition within the opening of the track. Such guide portion will be generally in alignment with the stem portions of the T-shaped elements. The above described angular movement of one of the T-shaped elements about the axis of its stem portion enables it to be moved to a position in which its transverse portion is generally in alignment with the guide portion, to pass through the opening of the track, whilst a 90xc2x0 movement of the T-shaped element about the axis of stem portion causes its transverse portion to extend laterally outwardly of the guide portion to enter the recesses of the track.
However if a guide portion is not provided the attachment member may be guided adequately by the T-shaped elements.
The T-shaped element which is movable lengthwise of its stem portion may be caused by such movement to assume a position in which its transverse portion is clear of the guide portion of the attachment member, so that with the attachment member as a whole extending transversely of the track the transverse portion of the T-shaped element may be passed through the opening into the track, after which movement of the attachment member through 90xc2x0 or thereabouts causes the transverse portion of the T-shaped element to extend laterally into the recesses of the track. The guide portion of the attachment member can then be moved into the opening to the track, and the T-shaped element returned, by movement lengthwise of its stem portion to the position in which its transverse portion lies in the vicinity of the guide portion of the attachment member, to hold the attachment member captive to the track. Thereafter the T-shaped element which is movable angularly about the axis of its stem portion can be moved so that its transverse portion also extends into the recesses of the track.
The attachment member is then guided for movement lengthwise of the track and held captive to the track by its guide portion and by the two transverse portions of the T-shaped elements. If the attachment member were not to be required to be movable lengthwise of the track, the dimensions and/or configuration of its T-shaped elements and/or guide portion may be such that the attachment member is held stationary relative to the track.
Preferably the T-shaped elements are resiliently biased to the positions they respectively assume when the attachment member is engaged with the track as aforesaid. Suitable springs or other resilient elements may operate on the T-shaped elements in the senses in which they are movable.
Preferably the locking means cooperates with the T-shaped elements to prevent their respective angular and lengthwise movements about their stem portions. The locking means may comprise a locking member which extends from the stem portion of the angularly moveable T-shaped element and is engageable with the stem portion of the axially movable T-shaped element.
The locking member may be provided on an arm extending transversely from an end portion of the stem of the angularly movable T-shaped element, the locking member being spring-biased radially away from the stem portion to be engageable with the stem portion of the axially-movable T-shaped element. It may engage beneath a head provided at the end of the stem portion of the axially movable T-shaped element, to prevent such axial movement thereof.
Yet a further aspect of the invention is concerned with the establishment of a connection, which may be detachable, between two elements disposed in end-to-end relationship with one another, which elements each have a lengthwise extending track formation. The track formation may be engageable, by an attachment member which may be moveable along the track formation in use, for connection to a safety element, as above referred to. Preferably the elongate elements are provided as part of or in association with respective structural truss members as referred to above.
This further aspect of the present invention is particularly advantageous in the context of an attachment member for a safety line connection, to enhance the freedom of movement of a person having a safety connection with a structural member in this way by providing for movement of the attachment member from the track formation of one elongate element to the track formation of a further elongate element connected end-to-end therewith, without any requirement for disconnection and re-connection.
According to a further aspect of the invention, therefore, we provide connecting means for establishing a releasable connection between two elements disposed adjacent one another, each said element being provided with a track formation for engagement by an attachment member, the connecting means affording a track means whereby said attachment member can move between the track formations of said elements whilst remaining captive.
Preferably the connecting means comprises two connecting elements, each adapted to be secured to one of said elements which are to be connected to one another, and said connecting elements being adapted to be releasably connected to one another and to afford said track means when thus connected.
Preferably each said connecting element affords a part of said track means. The connecting elements may be identical to one another.
Preferably each connecting element comprises spaced limbs which, when two connecting elements facing in opposite directions are placed together, intercalate so that holes in the limbs register for the insertion of a fastening element such as a retaining pin or bolt, by which the connecting elements are releasably secured together.
Each connecting element may comprise a spigot for reception in an opening in one of the elements which are being connected together, whereby the connecting elements are secured to said elements which are to be releasably connected together.
According to another aspect of the invention, we provide an assembly comprising two elements releasably connected together by connecting means according to the first aspect of the invention.
Preferably the elements which are releasably connected together are elongate elements, disposed in end to end relationship with one another.
Preferably the elements which are releasably connected together are elongate elements forming part of respective structural members, each comprising a number of elongate elements disposed in spaced generally parallel relationship with one another, with transversely extending elements therebetween.
All of the elongate elements in each structural truss may have a track formation as aforesaid, or only some thereof may be thus provided.
According to another aspect of the invention, we provide a structural member comprising a number of elongate elements disposed in spaced generally parallel relationship to one another with transversely extending elements therebetween, at least one of said elongate elements being provided with a lengthwise-extending track formation for engagement by an attachment member; at least one of said elongate elements with a track formation being provided at its end with a connecting element for releasable connection to a further connecting element provided at the end of a corresponding elongate element of another structural truss disposed in end to end relationship with the first said truss, said connecting elements together defining a track means whereby said attachment member can move between the track formations of the connected elongate elements while remaining captive.
A connecting element as above set forth may be connectable, as an alternative to being connected to another connecting element, to a stop member which is adapted to block the track formation at the end of the elongate element, to prevent an attachment member engaged with the track formation from becoming disengaged from the track formation by lengthwise movement out of the end thereof.
The invention further provides, according to another aspect, a stop member engageable with a connecting element as above set forth, the stop member comprising a fixing portion adapted to be secured to the connecting element and a blocking portion adapted to block the track formation adjacent said connecting element.
The invention also provides, according to another aspect, an attachment member which is intended for connection of equipment or the like to a structural member at a fixed position without being readily movable along the track formation thereof, but which is able to be engaged with the track formation without being passed therealong from an open end.
The invention yet further provides a structural member having a further member connected thereto by an attachment member as above referred to.